Hidden Expensive Items
[Compaign map] crawl into the furnace, shoot it if you can't fit, go into the cave, eat banana.
450$ Antique Sword
There is no door to this one, to get it you're gonna have to break the wall shown in the screenshot.
400$ Pirate Dagger
It's in between two rooms upstairs hidden behind the wall.
400$ Bag Full of Cash
Get on the table and smash the ceiling down.
Get to the attic by breaking the ceiling.
On the roof, you can get there by climbing the highest corner and shooting the roof with the shotgun.